Concern for the welfare of random source dogs cage-confined for purposes of biomedical research has led to establishment of minimum standards for their housing. Standards are based upon the belief that a certain minimum cage space is essential to the physical and emotional well-being of the dog. This study examines the hypothesis that stresses of cage confinement may be reduced 1) by expanding the cage volume in relation to the dog, or 2) providing daily exercise periods outside the cage, or 3) providing both factors. The study divides itself into two components; one considers physiological changes, and the other behavioral changes. It is considered that physiological stress will appear in activity of adrenal gland and adrenergic nervous system, in elevated resting heart rate and elevated blood pressure, and that the immobilization of confinement will result in reduced bone mineral content and muscular changes from disuse. Stress effects upon behavior may include decline in assurance, increase in timidity, and development of self-destructive, bizarre, or stereotyped behavior. The study uses preconditioned pound-derived dogs of both sexes, ranging in weight form 25 to 40 pounds. Comparison groups are 1) restricted (50% reduced cage volume) vs. non-restricted (normal federal standard cage volume), 2) restricted with exercise vs. non-restricted with exercise, 3) restricted without exercise vs. restricted with exercise, and 4) non-restricted without exercise vs. non-restricted with exercise. Exercise periods are 30 minutes each 5 of 7 consecutive days of confinement. Physiological studies include body weight, resting heart rate, indirect blood pressure, plasma and urinary cortisol, urinary vanilmandelic acid and hydroxproline excretion, in vivo bone mineral analysis by radiation densitometry, and a spectrum of serum chemistries including alkaline phosphatase, creatine phosphokinase, calcium and phosphorus, hemoglobin, and blood urea nitrogen. Behaviorally, cage and open field responses are observed, as are responses to novel stimuli, including human interaction and interaction with other dogs.